Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$135.50	9.605%	$148.5148	$148.51	$148.50	$148.50
Purchase #2	$161.87	4.108%	$168.5196	$168.52	$168.50	$168.50
Purchase #3	$238.52	10.328%	$263.1543	$263.15	$263.15	$263.20
Purchase #4	$140.77	8.382%	$152.5693	$152.57	$152.55	$152.60
Purchase #5	$50.72	11.662%	$56.635	$56.64	$56.65	$56.60
Purchase #6	$60.62	7.403%	$65.1077	$65.11	$65.10	$65.10
Purchase #7	$10.98	3.145%	$11.3253	$11.33	$11.35	$11.30
7 purchase totals =	$798.98		$865.8260	$865.83	$865.80	$865.80